1. Field of the Invention
The present invention relates generally to an automatic transmission and more specifically to a transmission of the type wherein main and auxiliary gear trains are arranged in parallel with one another.
2. Description of the Prior Art
The Toyota Celica new model hand book published by the Toyota Jidosha Company in August 1986 discloses a transmission arrangement which includes primary and secondary gear trains. These gear trains are arranged such that the shaft axes of each are parallel with one another and the secondary gear train is operatively connected with a final drive gear by way of a counter shaft. One end of the counter shaft has an input gear which meshes with the output gear of the secondary gear train. The other end of the counter shaft carries an output gear which forms part of the final drive.
The output shaft of the primary gear train is placed in a drive connection with the input shaft of the secondary gear train by way of meshing output and input gears which are respectively mounted on the primary output and secondary input shafts.
The primary gear train is used to produce first, second and third speeds while the secondary gear train is used to add an overdrive gear or 4th speed.
The secondary gear train includes a planetary gear unit wherein one of the gear elements is operatively connected with a multi-plate brake and is used as a reaction element.
However, this arrangement has suffered from a drawback that, in order to use one of the gear elements of the secondary gear train as a reaction element, it is necessary to dispose the multi-plate brake element between the input and output gears thereof. This increases the length and weight of the shafts between said input and output gears.
Yet another problem has been encountered in that in order to combine a one-way clutch with the multi-plate brake, it is necessary to dispose the one-way clutch in a position which is parallel with the multi-plate element in the axial direction of the shaft. This of course aggravates the shaft length and weight problems.
A further drawback has been encountered in that it is necessary to provide a bearing about the outer periphery of the output gear of the final drive. This bearing requires a bearing cover to support the same. The bearing cover of course must have a diameter greater than the bearing which it supports and induces the problem that extreme care must be exercised when machining the transmission casing in order to prevent possible misalignment problems.